Smectites Montmorillonite

Smectites (Montmorillonites). Smectites are the 2 1 clay minerals that carry a lattice charge and characteristically expand when solvated with water and alcohols, notably ethylene glycol and glycerol. In earUer Uterature, the term montmorillonite was used for both the group (now smectite) and the particular member of the group in which Mg is a significant substituent for Al in the octahedral layer. Typical formulas are shown in Table 2. Less common smectites include volkhonskoite [12286-87-2] hich. contains Cr " medmontite [12419-74-8], Cu " andpimeUte [12420-74-5], (12). 

In the discussions that follow, the terms which will be used are montmorillonite = tetrasilicic expanding phase, dominantly octahedrally charged montmorillonites = the undefined expanding phase(s) dioctahedral or trioctahedral montmorillonite = smectite or saponite, respectively. 

Figure 17. Proposed phase relations where K is a mobile component and Al, Fe are immobile components at about 20°C and several atmosphere water pressure for aluminous and ferric-ferrous mica-smectite minerals. Symbols are as follows I illite G = non-expanding glauconite Ox = iron oxide Kaol = kaolinlte Mo montmorillonite smectite N nontronitic smectite MLAL aluminous illite-smectite interlayered minerals Mlpe = iron-rich glauconite mica-smectite interlayered mineral. Dashed lines 1, 2, and 3 indicate the path three different starting materials might take during the process of glauconitization. The process involves increase of potassium content and the attainment of an iron-rich octahedral layer in a mica structure.

Smectites (Montmorillonites). Smectites are the 2 I clay mlneruK that carry a lattice charge and characteristically expand when solvated with water and alcohols, notably ethylene glycol and glycerol. 

Montmorillonites (smectite clays) have structures resembling that of pyrophyllite but the structure is not electrically neutral. Exchangeable cations are located in interlamellar regions of the clay and, furthermore, the clay can be flocculated such that the plate-like crystals compact with parallel c-axes to give coherent layers. The smectites are then attractive materials with which to modify electrodes. 

Figure 9 Distribution of montmorillonite (smectite) abundance in the <2fim fraction of sediments in the world ocean, carbonate-free basis. (After Griffin JJ, Windom H and Goldberg ED (1968) The distribution of clay minerals in the world ocean. Deep-Sea Research 15 433-459.)...

Another member of the illite group is hydrous mica, in which the principal interlayer cation is K. A smectite you might encounter is montmorillonite smectites can expand by incorporating water or organics between the structural layers. Vermiculite is derived from the Latin vermiculare, which means to breed worms, and describes what appears to happen when the material is heated rapidly. Otherwise it is very similar to phlogopite mica. As you would guess, most of these minerals have complex chemical compositions. 

In recent years, the PLA nanocomposites based on layered silicates, such as montmorillonite, smectite and mica has been actively investigated due to their... 

For ameliorating ion exchange, montmorillonites (smectites) are especially useful. With respect to potassium binding, kaolinites bind the least, and, e.g., mica and illite, bind the most K" " (Low, 1975). 

Figure 27. Diffractometer curves of interstratified montmorillonitic (smectitic) clays from various levels at Albertina, South Africa (Heystek [1954]). Note sharpening of reflection in region of 20A as a result of glycol treatment.

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